# import numpy as np
# arr=np.random.rand(3,4)
# import numpy as np
# arr=np.random.randn(3,4)
# import numpy as np
# arr=np.random.randint(1,10,size=(3,4))
# import numpy as np
# arr=np.random.choice([1,2,3,4,5],size=(3,4))
# print(arr)


# import numpy as np
# arr=np.arange(4)
# print(arr)
# import numpy as np
# arr=np.arange(1,10,2)
# print(arr)
# import numpy as np
# arr=np.arange(1,10,2)
# print(arr)
# import numpy as np
# arr=np.arange(0,1,0.2)
# print(arr)
# import numpy as np
# arr=np.arange(5,0,-1)
# print(arr)

# # 左臂右开区间5
# import numpy as np
# arr=np.linspace(5,12,num=5,endpoint=False,retstep=True)
# print(arr)
# # 左臂右开区间为2到8元数个数为5个底数为二
# import numpy as np
# arr1=np.logspace(2,8,num=5,endpoint=False,base=2)
# print(arr1)